1. Field of the Invention
This invention relates to a method of manufacturing a semiconductor device, and particularly to a method of manufacturing a dielectric film suitable for use as a capacitor film of a capacitor installed on a semiconductor substrate.
2. Description of the Related Art
In a memory device such as a DRAM (Dynamic Random Access Memory), a memory capacitor composed of a capacitor and a select transistor for performing switching to the memory capacitor are formed on a semiconductor substrate as a cell unit.
The more the dielectric constant of the capacitor increases, the capacitor film of such a capacitor used for the memory device or communication LSI is more advantageous to a technique such as compactness in size or the like.
From this reason, attention is now focused on barium strontium titanate (Ba1xe2x88x92xSrxTiO3: where x satisfies the relations in 0xe2x89xa6xc3x97xe2x89xa61, and hereinafter called xe2x80x9cBSTxe2x80x9d), which is extremely high in dielectric constant as compared with a dielectric film like a silicon oxide film or silicon nitride film.
This type of BST film can be formed by a general CVD process or sputtering process. It has been known that as the temperature of a growth interface of the BST film increases, a BST film having a high dielectric constant can be obtained, and the dielectric constant of the resultant BST film is greatly reduced at a growth interface temperature that falls below 400xc2x0 C.
Therefore, the effective utilization of the BST film as the capacitor film needs to keep the growth interface of the BST film at a high temperature so as to grow a BST film having a high dielectric constant.
It is thus considered that the semiconductor substrate is heated by, for example, a heating coil source or the like over its entirety. However, various problems arise due to the diffusion of heat at components of the semiconductor device if the semiconductor substrate is heated over its entirety so as to obtain the high dielectric constant.
Particularly, for example, a communication LSI like a microwave monolithic IC using, as the semiconductor substrate, a compound semiconductor including a component such as GaAs easy to be free by heating will cause a great influence exerted on the semiconductor substrate by heating of the compound semiconductor.
Thus, since the semiconductor substrate cannot be sufficiently heated in the prior art even if the BST film whose dielectric constant is high, is incorporated therein as the capacitor film of the semiconductor device, the capacitor film indicative of the high dielectric constant could not be formed.
Therefore, a technique for forming a dielectric layer capable of providing a high dielectric constant without heating of the entire semiconductor substrate has been long-expected.
An object of this invention is to solve the above-described problems of the prior art and hence to adopt the following construction by noting that a dielectric material like a BST film has a growth interface temperature greatly affected by whether its crystal characteristic is good or bad, and a dielectric constant increased owing to an improvement in its crystal characteristic, a method of growing a dielectric film includes a sputtering process or plasma CVD process using a plasma atmosphere, and a method of heating the dielectric film includes a method of using particle energy in a plasma.
According to one aspect of this invention, there is thus provided a method of manufacturing a semiconductor device, comprising the following steps of:
growing a dielectric film composed of a dielectric material whose dielectric constant is improved by crystallization thereof, on a semiconductor substrate to utilize the dielectric film as a capacitor film; and
applying a voltage to the semiconductor substrate in a plasma atmosphere to increase a growth interface temperature upon growth of the dielectric film.
The method of growing the dielectric film includes a growth method using a plasma atmosphere as in the case of, for example, a sputtering process or plasma CVD process. When a voltage is applied to a semiconductor substrate under such a plasma atmosphere, the surface of the semiconductor substrate subjected to the plasma atmosphere, which corresponds to the surface thereof on which a dielectric material is stacked, is principally heated by particle energy in a plasma.
From this point of view, the surface portion of the semiconductor substrate, which serves as the growth interface of the dielectric film, can be selectively maintained at a temperature most suitable for crystallization of the dielectric film without the semiconductor substrate being entirely heated to a high temperature most suitable for crystallization of the dielectric film.
Thus, since the growth interface of the dielectric film can be kept in a suitable high-temperature state without incurring bad effects due to entire heating of the semiconductor device including the semiconductor substrate, a good-quality dielectric film excellent in crystal characteristic and high in dielectric constant can be formed.
All the required thickness dimensions of the dielectric film can be formed while the voltage is being applied to the semiconductor substrate. Alternatively, the thin-film layer of the dielectric film is formed by applying the voltage thereto and thereafter the thin-film layer excellent in crystal characteristic is used as a base layer, whereby the dielectric film can be grown on the base layer in a state in which the semiconductor substrate has been heated over its entirety by a heating means similar to that employed in the art.
Since the thin-film layer constituting the base layer is excellent in crystal characteristic, a dielectric film quite excellent in crystal characteristic and demonstrative of a comparatively high dielectric constant as compared with the prior art can be grown even if the dielectric film is grown on the base layer by heating the semiconductor substrate over its entirety so that the temperature of the thin-film layer reaches a comparatively low temperature similar to that employed in the art.
The two-stage growth method for applying the voltage to the semiconductor substrate only upon growth of the base layer is advantageous particularly to a device structure disadvantageous to the application of the voltage to the semiconductor substrate for a long time.
Typical embodiments of the present invention have been shown in brief. However, the various embodiments of the present application and specific configurations of these embodiments will be understood from the following description.